It can be useful to monitor a wellbore traversing a subterranean formation for a variety of reasons, including for safety, determining the presence and type of fluid downhole, determining whether one or more components are positioned properly downhole, determining which component should be run downhole, and otherwise determining the state of the wellbore environment. It can be difficult to monitor complicated wellbores, including those that have one or more deviated wellbores or multiple zones, and long wellbores, such as those extending one to three or more miles below sea level.
Various techniques have been used to monitor wellbore environments. One technique is a smart well implementation that includes positioning downhole a cord that has sensors. The sensors are electronic-based (e.g. powered by batteries or power from the cord) sensors that can detect well conditions and transmit signals through the cord to a receiver. The signals can represent information about the well conditions, such as the presence and source of water. The receiver can interpret the signals and output the information.
Some smart well implementations use resonant sensors positioned downhole that respond to electromagnetic energy transmitted from the surface via a transmission line. The resonant sensors respond to the electromagnetic energy and information about the well condition can be derived by processing the response signal.
Other techniques include running a wireline tool downhole to log the well and determine well conditions, such as the presence and type of fluid downhole, or using a wireless telemetry system by running battery-powered devices downhole to perform measurements and wirelessly transmit the signals to the surface. Another technique includes positioning an acoustical signal generating device downhole that transmits an acoustical signal through a medium and the acoustical signal can be received by a device at the surface. The device analyzes the acoustical properties of the signal to determine information about the medium by comparing the properties to known properties of the acoustical signal generated by the generating device downhole.
Although effective, these techniques use electronic-based components that have a limited lifespan in a downhole environment. Furthermore, it can be difficult to implement most of these techniques in complicated or long wellbores and in existing wellbores. Implementing at least the wireline tool, for example, requires shutting off the well to run the wireline tool and log the well.
Therefore, assemblies are desirable that can be used throughout more of the life of a well, that are easily useable in complicated or long wellbores, and/or that are implemented easily in existing wellbores.